// SPDX-License-Identifier: GPL-2.0
/*
 * linux/ipc/shm.c
 * Copyright (C) 1992, 1993 Krishna Balasubramanian
 *     Many improvements/fixes by Bruno Haible.
 * Replaced `struct shm_desc' by `struct vm_area_struct', July 1994.
 * Fixed the shm swap deallocation (shm_unuse()), August 1998 Andrea Arcangeli.
 *
 * /proc/sysvipc/shm support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
 * BIGMEM support, Andrea Arcangeli <andrea@suse.de>
 * SMP thread shm, Jean-Luc Boyard <jean-luc.boyard@siemens.fr>
 * HIGHMEM support, Ingo Molnar <mingo@redhat.com>
 * Make shmmax, shmall, shmmni sysctl'able, Christoph Rohland <cr@sap.com>
 * Shared /dev/zero support, Kanoj Sarcar <kanoj@sgi.com>
 * Move the mm functionality over to mm/shmem.c, Christoph Rohland <cr@sap.com>
 *
 * support for audit of ipc object properties and permission changes
 * Dustin Kirkland <dustin.kirkland@us.ibm.com>
 *
 * namespaces support
 * OpenVZ, SWsoft Inc.
 * Pavel Emelianov <xemul@openvz.org>
 *
 * Better ipc lock (kern_ipc_perm.lock) handling
 * Davidlohr Bueso <davidlohr.bueso@hp.com>, June 2013.
 */

#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/hugetlb.h>
#include <linux/shm.h>
#include <linux/init.h>
#include <linux/file.h>
#include <linux/mman.h>
#include <linux/shmem_fs.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/audit.h>
#include <linux/capability.h>
#include <linux/ptrace.h>
#include <linux/seq_file.h>
#include <linux/rwsem.h>
#include <linux/nsproxy.h>
#include <linux/mount.h>
#include <linux/ipc_namespace.h>
#include <linux/rhashtable.h>

#include <linux/uaccess.h>

#include "util.h"

struct shmid_kernel {
    struct kern_ipc_perm shm_perm;
    struct file *shm_file;
    unsigned long shm_nattch;
    unsigned long shm_segsz;
    time64_t shm_atim;
    time64_t shm_dtim;
    time64_t shm_ctim;
    struct pid *shm_cprid;
    struct pid *shm_lprid;
    struct user_struct *mlock_user;

    /* The task created the shm object.  NULL if the task is dead. */
    struct task_struct *shm_creator;
    struct list_head shm_clist; /* list by creator */
    struct ipc_namespace *ns;
} __randomize_layout;

/* shm_mode upper byte flags */
#define SHM_DEST 01000   /* segment will be destroyed on last detach */
#define SHM_LOCKED 02000 /* segment will not be swapped */

struct shm_file_data {
    int id;
    struct ipc_namespace *ns;
    struct file *file;
    const struct vm_operations_struct *vm_ops;
};

#define shm_file_data(file) (*((struct shm_file_data **)&(file)->private_data))

static const struct file_operations shm_file_operations;
static const struct vm_operations_struct shm_vm_ops;

#define shm_ids(ns) ((ns)->ids[IPC_SHM_IDS])

#define shm_unlock(shp) ipc_unlock(&(shp)->shm_perm)

static int newseg(struct ipc_namespace *, struct ipc_params *);
static void shm_open(struct vm_area_struct *vma);
static void shm_close(struct vm_area_struct *vma);
static void shm_destroy(struct ipc_namespace *ns, struct shmid_kernel *shp);
#ifdef CONFIG_PROC_FS
static int sysvipc_shm_proc_show(struct seq_file *s, void *it);
#endif

void shm_init_ns(struct ipc_namespace *ns)
{
    ns->shm_ctlmax = SHMMAX;
    ns->shm_ctlall = SHMALL;
    ns->shm_ctlmni = SHMMNI;
    ns->shm_rmid_forced = 0;
    ns->shm_tot = 0;
    ipc_init_ids(&shm_ids(ns));
}

/*
 * Called with shm_ids.rwsem (writer) and the shp structure locked.
 * Only shm_ids.rwsem remains locked on exit.
 */
static void do_shm_rmid(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
{
    struct shmid_kernel *shp;

    shp = container_of(ipcp, struct shmid_kernel, shm_perm);
    WARN_ON(ns != shp->ns);

    if (shp->shm_nattch) {
        shp->shm_perm.mode |= SHM_DEST;
        /* Do not find it any more */
        ipc_set_key_private(&shm_ids(ns), &shp->shm_perm);
        shm_unlock(shp);
    } else {
        shm_destroy(ns, shp);
    }
}

#ifdef CONFIG_IPC_NS
void shm_exit_ns(struct ipc_namespace *ns)
{
    free_ipcs(ns, &shm_ids(ns), do_shm_rmid);
    idr_destroy(&ns->ids[IPC_SHM_IDS].ipcs_idr);
    rhashtable_destroy(&ns->ids[IPC_SHM_IDS].key_ht);
}
#endif

static int __init ipc_ns_init(void)
{
    shm_init_ns(&init_ipc_ns);
    return 0;
}

pure_initcall(ipc_ns_init);

void __init shm_init(void)
{
    ipc_init_proc_interface("sysvipc/shm",
#if BITS_PER_LONG <= 32
                            "       key      shmid perms       size  cpid  lpid nattch   uid   gid  cuid  cgid      "
                            "atime      dtime      ctime        rss       swap\n",
#else
                            "       key      shmid perms                  size  cpid  lpid nattch   uid   gid  cuid  "
                            "cgid      atime      dtime      ctime                   rss                  swap\n",
#endif
                            IPC_SHM_IDS, sysvipc_shm_proc_show);
}

static inline struct shmid_kernel *shm_obtain_object(struct ipc_namespace *ns, int id)
{
    struct kern_ipc_perm *ipcp = ipc_obtain_object_idr(&shm_ids(ns), id);

    if (IS_ERR(ipcp)) {
        return ERR_CAST(ipcp);
    }

    return container_of(ipcp, struct shmid_kernel, shm_perm);
}

static inline struct shmid_kernel *shm_obtain_object_check(struct ipc_namespace *ns, int id)
{
    struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&shm_ids(ns), id);

    if (IS_ERR(ipcp)) {
        return ERR_CAST(ipcp);
    }

    return container_of(ipcp, struct shmid_kernel, shm_perm);
}

/*
 * shm_lock_(check_) routines are called in the paths where the rwsem
 * is not necessarily held.
 */
static inline struct shmid_kernel *shm_lock(struct ipc_namespace *ns, int id)
{
    struct kern_ipc_perm *ipcp;

    rcu_read_lock();
    ipcp = ipc_obtain_object_idr(&shm_ids(ns), id);
    if (IS_ERR(ipcp)) {
        goto err;
    }

    ipc_lock_object(ipcp);
    /*
     * ipc_rmid() may have already freed the ID while ipc_lock_object()
     * was spinning: here verify that the structure is still valid.
     * Upon races with RMID, return -EIDRM, thus indicating that
     * the ID points to a removed identifier.
     */
    if (ipc_valid_object(ipcp)) {
        /* return a locked ipc object upon success */
        return container_of(ipcp, struct shmid_kernel, shm_perm);
    }

    ipc_unlock_object(ipcp);
    ipcp = ERR_PTR(-EIDRM);
err:
    rcu_read_unlock();
    /*
     * Callers of shm_lock() must validate the status of the returned ipc
     * object pointer and error out as appropriate.
     */
    return ERR_CAST(ipcp);
}

static inline void shm_lock_by_ptr(struct shmid_kernel *ipcp)
{
    rcu_read_lock();
    ipc_lock_object(&ipcp->shm_perm);
}

static void shm_rcu_free(struct rcu_head *head)
{
    struct kern_ipc_perm *ptr = container_of(head, struct kern_ipc_perm, rcu);
    struct shmid_kernel *shp = container_of(ptr, struct shmid_kernel, shm_perm);
    security_shm_free(&shp->shm_perm);
    kvfree(shp);
}

/*
 * It has to be called with shp locked.
 * It must be called before ipc_rmid()
 */
static inline void shm_clist_rm(struct shmid_kernel *shp)
{
    struct task_struct *creator;

    /* ensure that shm_creator does not disappear */
    rcu_read_lock();

    /*
     * A concurrent exit_shm may do a list_del_init() as well.
     * Just do nothing if exit_shm already did the work
     */
    if (!list_empty(&shp->shm_clist)) {
        /*
         * shp->shm_creator is guaranteed to be valid *only*
         * if shp->shm_clist is not empty.
         */
        creator = shp->shm_creator;

        task_lock(creator);
        /*
         * list_del_init() is a nop if the entry was already removed
         * from the list.
         */
        list_del_init(&shp->shm_clist);
        task_unlock(creator);
    }
    rcu_read_unlock();
}

static inline void shm_rmid(struct shmid_kernel *s)
{
    shm_clist_rm(s);
    ipc_rmid(&shm_ids(s->ns), &s->shm_perm);
}

static int __shm_open(struct vm_area_struct *vma)
{
    struct file *file = vma->vm_file;
    struct shm_file_data *sfd = shm_file_data(file);
    struct shmid_kernel *shp;

    shp = shm_lock(sfd->ns, sfd->id);
    if (IS_ERR(shp)) {
        return PTR_ERR(shp);
    }

    if (shp->shm_file != sfd->file) {
        /* ID was reused */
        shm_unlock(shp);
        return -EINVAL;
    }

    shp->shm_atim = ktime_get_real_seconds();
    ipc_update_pid(&shp->shm_lprid, task_tgid(current));
    shp->shm_nattch++;
    shm_unlock(shp);
    return 0;
}

/* This is called by fork, once for every shm attach. */
static void shm_open(struct vm_area_struct *vma)
{
    int err = __shm_open(vma);
    /*
     * We raced in the idr lookup or with shm_destroy().
     * Either way, the ID is busted.
     */
    WARN_ON_ONCE(err);
}

/*
 * shm_destroy - free the struct shmid_kernel
 *
 * @ns: namespace
 * @shp: struct to free
 *
 * It has to be called with shp and shm_ids.rwsem (writer) locked,
 * but returns with shp unlocked and freed.
 */
static void shm_destroy(struct ipc_namespace *ns, struct shmid_kernel *shp)
{
    struct file *shm_file;

    shm_file = shp->shm_file;
    shp->shm_file = NULL;
    ns->shm_tot -= (shp->shm_segsz + PAGE_SIZE - 1) >> PAGE_SHIFT;
    shm_rmid(shp);
    shm_unlock(shp);
    if (!is_file_hugepages(shm_file)) {
        shmem_lock(shm_file, 0, shp->mlock_user);
    } else if (shp->mlock_user) {
        user_shm_unlock(i_size_read(file_inode(shm_file)), shp->mlock_user);
    }
    fput(shm_file);
    ipc_update_pid(&shp->shm_cprid, NULL);
    ipc_update_pid(&shp->shm_lprid, NULL);
    ipc_rcu_putref(&shp->shm_perm, shm_rcu_free);
}

/*
 * shm_may_destroy - identifies whether shm segment should be destroyed now
 *
 * Returns true if and only if there are no active users of the segment and
 * one of the following is true:
 *
 * 1) shmctl(id, IPC_RMID, NULL) was called for this shp
 *
 * 2) sysctl kernel.shm_rmid_forced is set to 1.
 */
static bool shm_may_destroy(struct shmid_kernel *shp)
{
    return (shp->shm_nattch == 0) &&
           (shp->ns->shm_rmid_forced ||
        (shp->shm_perm.mode & SHM_DEST));
}

/*
 * remove the attach descriptor vma.
 * free memory for segment if it is marked destroyed.
 * The descriptor has already been removed from the current->mm->mmap list
 * and will later be kfree()d.
 */
static void shm_close(struct vm_area_struct *vma)
{
    struct file *file = vma->vm_file;
    struct shm_file_data *sfd = shm_file_data(file);
    struct shmid_kernel *shp;
    struct ipc_namespace *ns = sfd->ns;

    down_write(&shm_ids(ns).rwsem);
    /* remove from the list of attaches of the shm segment */
    shp = shm_lock(ns, sfd->id);
    /*
     * We raced in the idr lookup or with shm_destroy().
     * Either way, the ID is busted.
     */
    if (WARN_ON_ONCE(IS_ERR(shp))) {
        goto done; /* no-op */
    }

    ipc_update_pid(&shp->shm_lprid, task_tgid(current));
    shp->shm_dtim = ktime_get_real_seconds();
    shp->shm_nattch--;
    if (shm_may_destroy(shp)) {
        shm_destroy(ns, shp);
    } else {
        shm_unlock(shp);
    }
done:
    up_write(&shm_ids(ns).rwsem);
}

/* Called with ns->shm_ids(ns).rwsem locked */
static int shm_try_destroy_orphaned(int id, void *p, void *data)
{
    struct ipc_namespace *ns = data;
    struct kern_ipc_perm *ipcp = p;
    struct shmid_kernel *shp = container_of(ipcp, struct shmid_kernel, shm_perm);

    /*
     * We want to destroy segments without users and with already
     * exit'ed originating process.
     *
     * As shp->* are changed under rwsem, it's safe to skip shp locking.
     */
    if (!list_empty(&shp->shm_clist)) {
        return 0;
    }

    if (shm_may_destroy(shp)) {
        shm_lock_by_ptr(shp);
        shm_destroy(ns, shp);
    }
    return 0;
}

void shm_destroy_orphaned(struct ipc_namespace *ns)
{
    down_write(&shm_ids(ns).rwsem);
    if (shm_ids(ns).in_use) {
        idr_for_each(&shm_ids(ns).ipcs_idr, &shm_try_destroy_orphaned, ns);
    }
    up_write(&shm_ids(ns).rwsem);
}

/* Locking assumes this will only be called with task == current */
void exit_shm(struct task_struct *task)
{
    for (;;) {
        struct shmid_kernel *shp;
        struct ipc_namespace *ns;

        task_lock(task);

        if (list_empty(&task->sysvshm.shm_clist)) {
            task_unlock(task);
            break;
        }

        shp = list_first_entry(&task->sysvshm.shm_clist, struct shmid_kernel,
                shm_clist);

        /*
         * 1) Get pointer to the ipc namespace. It is worth to say
         * that this pointer is guaranteed to be valid because
         * shp lifetime is always shorter than namespace lifetime
         * in which shp lives.
         * We taken task_lock it means that shp won't be freed.
         */
        ns = shp->ns;

        /*
         * 2) If kernel.shm_rmid_forced is not set then only keep track of
         * which shmids are orphaned, so that a later set of the sysctl
         * can clean them up.
         */
        if (!ns->shm_rmid_forced)
            goto unlink_continue;

        /*
         * 3) get a reference to the namespace.
         *    The refcount could be already 0. If it is 0, then
         *    the shm objects will be free by free_ipc_work().
         */
        ns = get_ipc_ns_not_zero(ns);
        if (!ns) {
unlink_continue:
            list_del_init(&shp->shm_clist);
            task_unlock(task);
            continue;
        }

        /*
         * 4) get a reference to shp.
         *   This cannot fail: shm_clist_rm() is called before
         *   ipc_rmid(), thus the refcount cannot be 0.
         */
        WARN_ON(!ipc_rcu_getref(&shp->shm_perm));

        /*
         * 5) unlink the shm segment from the list of segments
         *    created by current.
         *    This must be done last. After unlinking,
         *    only the refcounts obtained above prevent IPC_RMID
         *    from destroying the segment or the namespace.
         */
        list_del_init(&shp->shm_clist);

        task_unlock(task);

        /*
         * 6) we have all references
         *    Thus lock & if needed destroy shp.
         */
        down_write(&shm_ids(ns).rwsem);
        shm_lock_by_ptr(shp);
        /*
         * rcu_read_lock was implicitly taken in shm_lock_by_ptr, it's
         * safe to call ipc_rcu_putref here
         */
        ipc_rcu_putref(&shp->shm_perm, shm_rcu_free);

        if (ipc_valid_object(&shp->shm_perm)) {
            if (shm_may_destroy(shp))
                shm_destroy(ns, shp);
            else
                shm_unlock(shp);
        } else {
            /*
             * Someone else deleted the shp from namespace
             * idr/kht while we have waited.
             * Just unlock and continue.
             */
            shm_unlock(shp);
        }

        up_write(&shm_ids(ns).rwsem);
        put_ipc_ns(ns); /* paired with get_ipc_ns_not_zero */
    }
}

static vm_fault_t shm_fault(struct vm_fault *vmf)
{
    struct file *file = vmf->vma->vm_file;
    struct shm_file_data *sfd = shm_file_data(file);

    return sfd->vm_ops->fault(vmf);
}

static int shm_split(struct vm_area_struct *vma, unsigned long addr)
{
    struct file *file = vma->vm_file;
    struct shm_file_data *sfd = shm_file_data(file);

    if (sfd->vm_ops->split) {
        return sfd->vm_ops->split(vma, addr);
    }

    return 0;
}

static unsigned long shm_pagesize(struct vm_area_struct *vma)
{
    struct file *file = vma->vm_file;
    struct shm_file_data *sfd = shm_file_data(file);

    if (sfd->vm_ops->pagesize) {
        return sfd->vm_ops->pagesize(vma);
    }

    return PAGE_SIZE;
}

#ifdef CONFIG_NUMA
static int shm_set_policy(struct vm_area_struct *vma, struct mempolicy *new)
{
    struct file *file = vma->vm_file;
    struct shm_file_data *sfd = shm_file_data(file);
    int err = 0;

    if (sfd->vm_ops->set_policy) {
        err = sfd->vm_ops->set_policy(vma, new);
    }
    return err;
}

static struct mempolicy *shm_get_policy(struct vm_area_struct *vma, unsigned long addr)
{
    struct file *file = vma->vm_file;
    struct shm_file_data *sfd = shm_file_data(file);
    struct mempolicy *pol = NULL;

    if (sfd->vm_ops->get_policy) {
        pol = sfd->vm_ops->get_policy(vma, addr);
    } else if (vma->vm_policy) {
        pol = vma->vm_policy;
    }

    return pol;
}
#endif

static int shm_mmap(struct file *file, struct vm_area_struct *vma)
{
    struct shm_file_data *sfd = shm_file_data(file);
    int ret;

    /*
     * In case of remap_file_pages() emulation, the file can represent an
     * IPC ID that was removed, and possibly even reused by another shm
     * segment already.  Propagate this case as an error to caller.
     */
    ret = __shm_open(vma);
    if (ret) {
        return ret;
    }

    ret = call_mmap(sfd->file, vma);
    if (ret) {
        shm_close(vma);
        return ret;
    }
    sfd->vm_ops = vma->vm_ops;
#ifdef CONFIG_MMU
    WARN_ON(!sfd->vm_ops->fault);
#endif
    vma->vm_ops = &shm_vm_ops;
    return 0;
}

static int shm_release(struct inode *ino, struct file *file)
{
    struct shm_file_data *sfd = shm_file_data(file);

    put_ipc_ns(sfd->ns);
    fput(sfd->file);
    shm_file_data(file) = NULL;
    kfree(sfd);
    return 0;
}

static int shm_fsync(struct file *file, loff_t start, loff_t end, int datasync)
{
    struct shm_file_data *sfd = shm_file_data(file);

    if (!sfd->file->f_op->fsync) {
        return -EINVAL;
    }
    return sfd->file->f_op->fsync(sfd->file, start, end, datasync);
}

static long shm_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
{
    struct shm_file_data *sfd = shm_file_data(file);

    if (!sfd->file->f_op->fallocate) {
        return -EOPNOTSUPP;
    }
    return sfd->file->f_op->fallocate(file, mode, offset, len);
}

static unsigned long shm_get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
                                           unsigned long pgoff, unsigned long flags)
{
    struct shm_file_data *sfd = shm_file_data(file);

    return sfd->file->f_op->get_unmapped_area(sfd->file, addr, len, pgoff, flags);
}

static const struct file_operations shm_file_operations = {
    .mmap = shm_mmap,
    .fsync = shm_fsync,
    .release = shm_release,
    .get_unmapped_area = shm_get_unmapped_area,
    .llseek = noop_llseek,
    .fallocate = shm_fallocate,
};

/*
 * shm_file_operations_huge is now identical to shm_file_operations,
 * but we keep it distinct for the sake of is_file_shm_hugepages().
 */
static const struct file_operations shm_file_operations_huge = {
    .mmap = shm_mmap,
    .fsync = shm_fsync,
    .release = shm_release,
    .get_unmapped_area = shm_get_unmapped_area,
    .llseek = noop_llseek,
    .fallocate = shm_fallocate,
};

bool is_file_shm_hugepages(struct file *file)
{
    return file->f_op == &shm_file_operations_huge;
}

static const struct vm_operations_struct shm_vm_ops = {
    .open = shm_open,   /* callback for a new vm-area open */
    .close = shm_close, /* callback for when the vm-area is released */
    .fault = shm_fault,
    .split = shm_split,
    .pagesize = shm_pagesize,
#if defined(CONFIG_NUMA)
    .set_policy = shm_set_policy,
    .get_policy = shm_get_policy,
#endif
};

/**
 * newseg - Create a new shared memory segment
 * @ns: namespace
 * @params: ptr to the structure that contains key, size and shmflg
 *
 * Called with shm_ids.rwsem held as a writer.
 */
static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
{
    key_t key = params->key;
    int shmflg = params->flg;
    size_t size = params->u.size;
    int error;
    struct shmid_kernel *shp;
    size_t numpages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
    struct file *file;
    char name[13];
    vm_flags_t acctflag = 0;

    if (size < SHMMIN || size > ns->shm_ctlmax) {
        return -EINVAL;
    }

    if ((numpages << PAGE_SHIFT) < size) {
        return -ENOSPC;
    }

    if (ns->shm_tot + numpages < ns->shm_tot || ns->shm_tot + numpages > ns->shm_ctlall) {
        return -ENOSPC;
    }

    shp = kvmalloc(sizeof(*shp), GFP_KERNEL);
    if (unlikely(!shp)) {
        return -ENOMEM;
    }

    shp->shm_perm.key = key;
    shp->shm_perm.mode = (shmflg & S_IRWXUGO);
    shp->mlock_user = NULL;

    shp->shm_perm.security = NULL;
    error = security_shm_alloc(&shp->shm_perm);
    if (error) {
        kvfree(shp);
        return error;
    }

    (void)sprintf(name, "SYSV%08x", key);
    if (shmflg & SHM_HUGETLB) {
        struct hstate *hs;
        size_t hugesize;

        hs = hstate_sizelog((shmflg >> SHM_HUGE_SHIFT) & SHM_HUGE_MASK);
        if (!hs) {
            error = -EINVAL;
            goto no_file;
        }
        hugesize = ALIGN(size, huge_page_size(hs));

        /* hugetlb_file_setup applies strict accounting */
        if (shmflg & SHM_NORESERVE) {
            acctflag = VM_NORESERVE;
        }
        file = hugetlb_file_setup(name, hugesize, acctflag, &shp->mlock_user, HUGETLB_SHMFS_INODE,
                                  (shmflg >> SHM_HUGE_SHIFT) & SHM_HUGE_MASK);
    } else {
        /*
         * Do not allow no accounting for OVERCOMMIT_NEVER, even
         * if it's asked for.
         */
        if ((shmflg & SHM_NORESERVE) && sysctl_overcommit_memory != OVERCOMMIT_NEVER) {
            acctflag = VM_NORESERVE;
        }
        file = shmem_kernel_file_setup(name, size, acctflag);
    }
    error = PTR_ERR(file);
    if (IS_ERR(file)) {
        goto no_file;
    }

    shp->shm_cprid = get_pid(task_tgid(current));
    shp->shm_lprid = NULL;
    shp->shm_atim = shp->shm_dtim = 0;
    shp->shm_ctim = ktime_get_real_seconds();
    shp->shm_segsz = size;
    shp->shm_nattch = 0;
    shp->shm_file = file;
    shp->shm_creator = current;

    /* ipc_addid() locks shp upon success. */
    error = ipc_addid(&shm_ids(ns), &shp->shm_perm, ns->shm_ctlmni);
    if (error < 0) {
        goto no_id;
    }
    shp->ns = ns;

    task_lock(current);
    list_add(&shp->shm_clist, &current->sysvshm.shm_clist);
    task_unlock(current);

    /*
     * shmid gets reported as "inode#" in /proc/pid/maps.
     * proc-ps tools use this. Changing this will break them.
     */
    file_inode(file)->i_ino = shp->shm_perm.id;

    ns->shm_tot += numpages;
    error = shp->shm_perm.id;

    ipc_unlock_object(&shp->shm_perm);
    rcu_read_unlock();
    return error;

no_id:
    ipc_update_pid(&shp->shm_cprid, NULL);
    ipc_update_pid(&shp->shm_lprid, NULL);
    if (is_file_hugepages(file) && shp->mlock_user) {
        user_shm_unlock(size, shp->mlock_user);
    }
    fput(file);
    ipc_rcu_putref(&shp->shm_perm, shm_rcu_free);
    return error;
no_file:
    call_rcu(&shp->shm_perm.rcu, shm_rcu_free);
    return error;
}

/*
 * Called with shm_ids.rwsem and ipcp locked.
 */
static int shm_more_checks(struct kern_ipc_perm *ipcp, struct ipc_params *params)
{
    struct shmid_kernel *shp;

    shp = container_of(ipcp, struct shmid_kernel, shm_perm);
    if (shp->shm_segsz < params->u.size) {
        return -EINVAL;
    }

    return 0;
}

long ksys_shmget(key_t key, size_t size, int shmflg)
{
    struct ipc_namespace *ns;
    static const struct ipc_ops shm_ops = {
        .getnew = newseg,
        .associate = security_shm_associate,
        .more_checks = shm_more_checks,
    };
    struct ipc_params shm_params;

    ns = current->nsproxy->ipc_ns;

    shm_params.key = key;
    shm_params.flg = shmflg;
    shm_params.u.size = size;

    return ipcget(ns, &shm_ids(ns), &shm_ops, &shm_params);
}

SYSCALL_DEFINE3(shmget, key_t, key, size_t, size, int, shmflg)
{
    return ksys_shmget(key, size, shmflg);
}

static inline unsigned long copy_shmid_to_user(void __user *buf, struct shmid64_ds *in, int version)
{
    switch (version) {
        case IPC_64:
            return copy_to_user(buf, in, sizeof(*in));
        case IPC_OLD: {
            struct shmid_ds out;

            memset(&out, 0, sizeof(out));
            ipc64_perm_to_ipc_perm(&in->shm_perm, &out.shm_perm);
            out.shm_segsz = in->shm_segsz;
            out.shm_atime = in->shm_atime;
            out.shm_dtime = in->shm_dtime;
            out.shm_ctime = in->shm_ctime;
            out.shm_cpid = in->shm_cpid;
            out.shm_lpid = in->shm_lpid;
            out.shm_nattch = in->shm_nattch;

            return copy_to_user(buf, &out, sizeof(out));
        }
        default:
            return -EINVAL;
    }
}

static inline unsigned long copy_shmid_from_user(struct shmid64_ds *out, void __user *buf, int version)
{
    switch (version) {
        case IPC_64:
            if (copy_from_user(out, buf, sizeof(*out))) {
                return -EFAULT;
            }
            return 0;
        case IPC_OLD: {
            struct shmid_ds tbuf_old;

            if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old))) {
                return -EFAULT;
            }

            out->shm_perm.uid = tbuf_old.shm_perm.uid;
            out->shm_perm.gid = tbuf_old.shm_perm.gid;
            out->shm_perm.mode = tbuf_old.shm_perm.mode;

            return 0;
        }
        default:
            return -EINVAL;
    }
}

static inline unsigned long copy_shminfo_to_user(void __user *buf, struct shminfo64 *in, int version)
{
    switch (version) {
        case IPC_64:
            return copy_to_user(buf, in, sizeof(*in));
        case IPC_OLD: {
            struct shminfo out;

            if (in->shmmax > INT_MAX) {
                out.shmmax = INT_MAX;
            } else {
                out.shmmax = (int)in->shmmax;
            }

            out.shmmin = in->shmmin;
            out.shmmni = in->shmmni;
            out.shmseg = in->shmseg;
            out.shmall = in->shmall;

            return copy_to_user(buf, &out, sizeof(out));
        }
        default:
            return -EINVAL;
    }
}

/*
 * Calculate and add used RSS and swap pages of a shm.
 * Called with shm_ids.rwsem held as a reader
 */
static void shm_add_rss_swap(struct shmid_kernel *shp, unsigned long *rss_add, unsigned long *swp_add)
{
    struct inode *inode;

    inode = file_inode(shp->shm_file);

    if (is_file_hugepages(shp->shm_file)) {
        struct address_space *mapping = inode->i_mapping;
        struct hstate *h = hstate_file(shp->shm_file);
        *rss_add += pages_per_huge_page(h) * mapping->nrpages;
    } else {
#ifdef CONFIG_SHMEM
        struct shmem_inode_info *info = SHMEM_I(inode);

        spin_lock_irq(&info->lock);
        *rss_add += inode->i_mapping->nrpages;
        *swp_add += info->swapped;
        spin_unlock_irq(&info->lock);
#else
        *rss_add += inode->i_mapping->nrpages;
#endif
    }
}

/*
 * Called with shm_ids.rwsem held as a reader
 */
static void shm_get_stat(struct ipc_namespace *ns, unsigned long *rss, unsigned long *swp)
{
    int next_id;
    int total, in_use;

    *rss = 0;
    *swp = 0;

    in_use = shm_ids(ns).in_use;

    for (total = 0, next_id = 0; total < in_use; next_id++) {
        struct kern_ipc_perm *ipc;
        struct shmid_kernel *shp;

        ipc = idr_find(&shm_ids(ns).ipcs_idr, next_id);
        if (ipc == NULL) {
            continue;
        }
        shp = container_of(ipc, struct shmid_kernel, shm_perm);

        shm_add_rss_swap(shp, rss, swp);

        total++;
    }
}

/*
 * This function handles some shmctl commands which require the rwsem
 * to be held in write mode.
 * NOTE: no locks must be held, the rwsem is taken inside this function.
 */
static int shmctl_down(struct ipc_namespace *ns, int shmid, int cmd, struct shmid64_ds *shmid64)
{
    struct kern_ipc_perm *ipcp;
    struct shmid_kernel *shp;
    int err;

    down_write(&shm_ids(ns).rwsem);
    rcu_read_lock();

    ipcp = ipcctl_obtain_check(ns, &shm_ids(ns), shmid, cmd, &shmid64->shm_perm, 0);
    if (IS_ERR(ipcp)) {
        err = PTR_ERR(ipcp);
        goto out_unlock1;
    }

    shp = container_of(ipcp, struct shmid_kernel, shm_perm);

    err = security_shm_shmctl(&shp->shm_perm, cmd);
    if (err) {
        goto out_unlock1;
    }

    switch (cmd) {
        case IPC_RMID:
            ipc_lock_object(&shp->shm_perm);
            /* do_shm_rmid unlocks the ipc object and rcu */
            do_shm_rmid(ns, ipcp);
            goto out_up;
        case IPC_SET:
            ipc_lock_object(&shp->shm_perm);
            err = ipc_update_perm(&shmid64->shm_perm, ipcp);
            if (err) {
                goto out_unlock0;
            }
            shp->shm_ctim = ktime_get_real_seconds();
            break;
        default:
            err = -EINVAL;
            goto out_unlock1;
    }

out_unlock0:
    ipc_unlock_object(&shp->shm_perm);
out_unlock1:
    rcu_read_unlock();
out_up:
    up_write(&shm_ids(ns).rwsem);
    return err;
}

static int shmctl_ipc_info(struct ipc_namespace *ns, struct shminfo64 *shminfo)
{
    int err = security_shm_shmctl(NULL, IPC_INFO);
    if (!err) {
        memset(shminfo, 0, sizeof(*shminfo));
        shminfo->shmmni = shminfo->shmseg = ns->shm_ctlmni;
        shminfo->shmmax = ns->shm_ctlmax;
        shminfo->shmall = ns->shm_ctlall;
        shminfo->shmmin = SHMMIN;
        down_read(&shm_ids(ns).rwsem);
        err = ipc_get_maxidx(&shm_ids(ns));
        up_read(&shm_ids(ns).rwsem);
        if (err < 0) {
            err = 0;
        }
    }
    return err;
}

static int shmctl_shm_info(struct ipc_namespace *ns, struct shm_info *shm_info)
{
    int err = security_shm_shmctl(NULL, SHM_INFO);
    if (!err) {
        memset(shm_info, 0, sizeof(*shm_info));
        down_read(&shm_ids(ns).rwsem);
        shm_info->used_ids = shm_ids(ns).in_use;
        shm_get_stat(ns, &shm_info->shm_rss, &shm_info->shm_swp);
        shm_info->shm_tot = ns->shm_tot;
        shm_info->swap_attempts = 0;
        shm_info->swap_successes = 0;
        err = ipc_get_maxidx(&shm_ids(ns));
        up_read(&shm_ids(ns).rwsem);
        if (err < 0) {
            err = 0;
        }
    }
    return err;
}

static int shmctl_stat(struct ipc_namespace *ns, int shmid, int cmd, struct shmid64_ds *tbuf)
{
    struct shmid_kernel *shp;
    int err;

    memset(tbuf, 0, sizeof(*tbuf));

    rcu_read_lock();
    if (cmd == SHM_STAT || cmd == SHM_STAT_ANY) {
        shp = shm_obtain_object(ns, shmid);
        if (IS_ERR(shp)) {
            err = PTR_ERR(shp);
            goto out_unlock;
        }
    } else { /* IPC_STAT */
        shp = shm_obtain_object_check(ns, shmid);
        if (IS_ERR(shp)) {
            err = PTR_ERR(shp);
            goto out_unlock;
        }
    }

    /*
     * Semantically SHM_STAT_ANY ought to be identical to
     * that functionality provided by the /proc/sysvipc/
     * interface. As such, only audit these calls and
     * do not do traditional S_IRUGO permission checks on
     * the ipc object.
     */
    if (cmd == SHM_STAT_ANY) {
        audit_ipc_obj(&shp->shm_perm);
    } else {
        err = -EACCES;
        if (ipcperms(ns, &shp->shm_perm, S_IRUGO)) {
            goto out_unlock;
        }
    }

    err = security_shm_shmctl(&shp->shm_perm, cmd);
    if (err) {
        goto out_unlock;
    }

    ipc_lock_object(&shp->shm_perm);

    if (!ipc_valid_object(&shp->shm_perm)) {
        ipc_unlock_object(&shp->shm_perm);
        err = -EIDRM;
        goto out_unlock;
    }

    kernel_to_ipc64_perm(&shp->shm_perm, &tbuf->shm_perm);
    tbuf->shm_segsz = shp->shm_segsz;
    tbuf->shm_atime = shp->shm_atim;
    tbuf->shm_dtime = shp->shm_dtim;
    tbuf->shm_ctime = shp->shm_ctim;
#ifndef CONFIG_64BIT
    tbuf->shm_atime_high = shp->shm_atim >> 0x20;
    tbuf->shm_dtime_high = shp->shm_dtim >> 0x20;
    tbuf->shm_ctime_high = shp->shm_ctim >> 0x20;
#endif
    tbuf->shm_cpid = pid_vnr(shp->shm_cprid);
    tbuf->shm_lpid = pid_vnr(shp->shm_lprid);
    tbuf->shm_nattch = shp->shm_nattch;

    if (cmd == IPC_STAT) {
        /*
         * As defined in SUS:
         * Return 0 on success
         */
        err = 0;
    } else {
        /*
         * SHM_STAT and SHM_STAT_ANY (both Linux specific)
         * Return the full id, including the sequence number
         */
        err = shp->shm_perm.id;
    }

    ipc_unlock_object(&shp->shm_perm);
out_unlock:
    rcu_read_unlock();
    return err;
}

static int shmctl_do_lock(struct ipc_namespace *ns, int shmid, int cmd)
{
    struct shmid_kernel *shp;
    struct file *shm_file;
    int err;

    rcu_read_lock();
    shp = shm_obtain_object_check(ns, shmid);
    if (IS_ERR(shp)) {
        err = PTR_ERR(shp);
        goto out_unlock1;
    }

    audit_ipc_obj(&(shp->shm_perm));
    err = security_shm_shmctl(&shp->shm_perm, cmd);
    if (err) {
        goto out_unlock1;
    }

    ipc_lock_object(&shp->shm_perm);

    /* check if shm_destroy() is tearing down shp */
    if (!ipc_valid_object(&shp->shm_perm)) {
        err = -EIDRM;
        goto out_unlock0;
    }

    if (!ns_capable(ns->user_ns, CAP_IPC_LOCK)) {
        kuid_t euid = current_euid();
        if (!uid_eq(euid, shp->shm_perm.uid) && !uid_eq(euid, shp->shm_perm.cuid)) {
            err = -EPERM;
            goto out_unlock0;
        }
        if (cmd == SHM_LOCK && !rlimit(RLIMIT_MEMLOCK)) {
            err = -EPERM;
            goto out_unlock0;
        }
    }

    shm_file = shp->shm_file;
    if (is_file_hugepages(shm_file)) {
        goto out_unlock0;
    }

    if (cmd == SHM_LOCK) {
        struct user_struct *user = current_user();

        err = shmem_lock(shm_file, 1, user);
        if (!err && !(shp->shm_perm.mode & SHM_LOCKED)) {
            shp->shm_perm.mode |= SHM_LOCKED;
            shp->mlock_user = user;
        }
        goto out_unlock0;
    }

    /* SHM_UNLOCK */
    if (!(shp->shm_perm.mode & SHM_LOCKED)) {
        goto out_unlock0;
    }
    shmem_lock(shm_file, 0, shp->mlock_user);
    shp->shm_perm.mode &= ~SHM_LOCKED;
    shp->mlock_user = NULL;
    get_file(shm_file);
    ipc_unlock_object(&shp->shm_perm);
    rcu_read_unlock();
    shmem_unlock_mapping(shm_file->f_mapping);

    fput(shm_file);
    return err;

out_unlock0:
    ipc_unlock_object(&shp->shm_perm);
out_unlock1:
    rcu_read_unlock();
    return err;
}

static long ksys_shmctl(int shmid, int cmd, struct shmid_ds __user *buf, int version)
{
    int err;
    struct ipc_namespace *ns;
    struct shmid64_ds sem64;

    if (cmd < 0 || shmid < 0) {
        return -EINVAL;
    }

    ns = current->nsproxy->ipc_ns;

    switch (cmd) {
        case IPC_INFO: {
            struct shminfo64 shminfo;
            err = shmctl_ipc_info(ns, &shminfo);
            if (err < 0) {
                return err;
            }
            if (copy_shminfo_to_user(buf, &shminfo, version)) {
                err = -EFAULT;
            }
            return err;
        }
        case SHM_INFO: {
            struct shm_info shm_info;
            err = shmctl_shm_info(ns, &shm_info);
            if (err < 0) {
                return err;
            }
            if (copy_to_user(buf, &shm_info, sizeof(shm_info))) {
                err = -EFAULT;
            }
            return err;
        }
        case SHM_STAT:
        case SHM_STAT_ANY:
        case IPC_STAT: {
            err = shmctl_stat(ns, shmid, cmd, &sem64);
            if (err < 0) {
                return err;
            }
            if (copy_shmid_to_user(buf, &sem64, version)) {
                err = -EFAULT;
            }
            return err;
        }
        case IPC_SET:
            if (copy_shmid_from_user(&sem64, buf, version)) {
                return -EFAULT;
            }
            fallthrough;
        case IPC_RMID:
            return shmctl_down(ns, shmid, cmd, &sem64);
        case SHM_LOCK:
        case SHM_UNLOCK:
            return shmctl_do_lock(ns, shmid, cmd);
        default:
            return -EINVAL;
    }
}

SYSCALL_DEFINE3(shmctl, int, shmid, int, cmd, struct shmid_ds __user *, buf)
{
    return ksys_shmctl(shmid, cmd, buf, IPC_64);
}

#ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION
long ksys_old_shmctl(int shmid, int cmd, struct shmid_ds __user *buf)
{
    int version = ipc_parse_version(&cmd);

    return ksys_shmctl(shmid, cmd, buf, version);
}

SYSCALL_DEFINE3(old_shmctl, int, shmid, int, cmd, struct shmid_ds __user *, buf)
{
    return ksys_old_shmctl(shmid, cmd, buf);
}
#endif

#ifdef CONFIG_COMPAT

struct compat_shmid_ds {
    struct compat_ipc_perm shm_perm;
    int shm_segsz;
    old_time32_t shm_atime;
    old_time32_t shm_dtime;
    old_time32_t shm_ctime;
    compat_ipc_pid_t shm_cpid;
    compat_ipc_pid_t shm_lpid;
    unsigned short shm_nattch;
    unsigned short shm_unused;
    compat_uptr_t shm_unused2;
    compat_uptr_t shm_unused3;
};

struct compat_shminfo64 {
    compat_ulong_t shmmax;
    compat_ulong_t shmmin;
    compat_ulong_t shmmni;
    compat_ulong_t shmseg;
    compat_ulong_t shmall;
    compat_ulong_t __unused1;
    compat_ulong_t __unused2;
    compat_ulong_t __unused3;
    compat_ulong_t __unused4;
};

struct compat_shm_info {
    compat_int_t used_ids;
    compat_ulong_t shm_tot, shm_rss, shm_swp;
    compat_ulong_t swap_attempts, swap_successes;
};

static int copy_compat_shminfo_to_user(void __user *buf, struct shminfo64 *in, int version)
{
    if (in->shmmax > INT_MAX) {
        in->shmmax = INT_MAX;
    }
    if (version == IPC_64) {
        struct compat_shminfo64 info;
        memset(&info, 0, sizeof(info));
        info.shmmax = in->shmmax;
        info.shmmin = in->shmmin;
        info.shmmni = in->shmmni;
        info.shmseg = in->shmseg;
        info.shmall = in->shmall;
        return copy_to_user(buf, &info, sizeof(info));
    } else {
        struct shminfo info;
        memset(&info, 0, sizeof(info));
        info.shmmax = in->shmmax;
        info.shmmin = in->shmmin;
        info.shmmni = in->shmmni;
        info.shmseg = in->shmseg;
        info.shmall = in->shmall;
        return copy_to_user(buf, &info, sizeof(info));
    }
}

static int put_compat_shm_info(struct shm_info *ip, struct compat_shm_info __user *uip)
{
    struct compat_shm_info info;

    memset(&info, 0, sizeof(info));
    info.used_ids = ip->used_ids;
    info.shm_tot = ip->shm_tot;
    info.shm_rss = ip->shm_rss;
    info.shm_swp = ip->shm_swp;
    info.swap_attempts = ip->swap_attempts;
    info.swap_successes = ip->swap_successes;
    return copy_to_user(uip, &info, sizeof(info));
}

static int copy_compat_shmid_to_user(void __user *buf, struct shmid64_ds *in, int version)
{
    if (version == IPC_64) {
        struct compat_shmid64_ds v;
        memset(&v, 0, sizeof(v));
        to_compat_ipc64_perm(&v.shm_perm, &in->shm_perm);
        v.shm_atime = lower_32_bits(in->shm_atime);
        v.shm_atime_high = upper_32_bits(in->shm_atime);
        v.shm_dtime = lower_32_bits(in->shm_dtime);
        v.shm_dtime_high = upper_32_bits(in->shm_dtime);
        v.shm_ctime = lower_32_bits(in->shm_ctime);
        v.shm_ctime_high = upper_32_bits(in->shm_ctime);
        v.shm_segsz = in->shm_segsz;
        v.shm_nattch = in->shm_nattch;
        v.shm_cpid = in->shm_cpid;
        v.shm_lpid = in->shm_lpid;
        return copy_to_user(buf, &v, sizeof(v));
    } else {
        struct compat_shmid_ds v;
        memset(&v, 0, sizeof(v));
        to_compat_ipc_perm(&v.shm_perm, &in->shm_perm);
        v.shm_perm.key = in->shm_perm.key;
        v.shm_atime = in->shm_atime;
        v.shm_dtime = in->shm_dtime;
        v.shm_ctime = in->shm_ctime;
        v.shm_segsz = in->shm_segsz;
        v.shm_nattch = in->shm_nattch;
        v.shm_cpid = in->shm_cpid;
        v.shm_lpid = in->shm_lpid;
        return copy_to_user(buf, &v, sizeof(v));
    }
}

static int copy_compat_shmid_from_user(struct shmid64_ds *out, void __user *buf, int version)
{
    memset(out, 0, sizeof(*out));
    if (version == IPC_64) {
        struct compat_shmid64_ds __user *p = buf;
        return get_compat_ipc64_perm(&out->shm_perm, &p->shm_perm);
    } else {
        struct compat_shmid_ds __user *p = buf;
        return get_compat_ipc_perm(&out->shm_perm, &p->shm_perm);
    }
}

static long compat_ksys_shmctl(int shmid, int cmd, void __user *uptr, int version)
{
    struct ipc_namespace *ns;
    struct shmid64_ds sem64;
    int err;

    ns = current->nsproxy->ipc_ns;

    if (cmd < 0 || shmid < 0) {
        return -EINVAL;
    }

    switch (cmd) {
        case IPC_INFO: {
            struct shminfo64 shminfo;
            err = shmctl_ipc_info(ns, &shminfo);
            if (err < 0) {
                return err;
            }
            if (copy_compat_shminfo_to_user(uptr, &shminfo, version)) {
                err = -EFAULT;
            }
            return err;
        }
        case SHM_INFO: {
            struct shm_info shm_info;
            err = shmctl_shm_info(ns, &shm_info);
            if (err < 0) {
                return err;
            }
            if (put_compat_shm_info(&shm_info, uptr)) {
                err = -EFAULT;
            }
            return err;
        }
        case IPC_STAT:
        case SHM_STAT_ANY:
        case SHM_STAT:
            err = shmctl_stat(ns, shmid, cmd, &sem64);
            if (err < 0) {
                return err;
            }
            if (copy_compat_shmid_to_user(uptr, &sem64, version)) {
                err = -EFAULT;
            }
            return err;

        case IPC_SET:
            if (copy_compat_shmid_from_user(&sem64, uptr, version)) {
                return -EFAULT;
            }
            fallthrough;
        case IPC_RMID:
            return shmctl_down(ns, shmid, cmd, &sem64);
        case SHM_LOCK:
        case SHM_UNLOCK:
            return shmctl_do_lock(ns, shmid, cmd);
        default:
            return -EINVAL;
    }
    return err;
}

COMPAT_SYSCALL_DEFINE3(shmctl, int, shmid, int, cmd, void __user *, uptr)
{
    return compat_ksys_shmctl(shmid, cmd, uptr, IPC_64);
}

#ifdef CONFIG_ARCH_WANT_COMPAT_IPC_PARSE_VERSION
long compat_ksys_old_shmctl(int shmid, int cmd, void __user *uptr)
{
    int version = compat_ipc_parse_version(&cmd);

    return compat_ksys_shmctl(shmid, cmd, uptr, version);
}

COMPAT_SYSCALL_DEFINE3(old_shmctl, int, shmid, int, cmd, void __user *, uptr)
{
    return compat_ksys_old_shmctl(shmid, cmd, uptr);
}
#endif
#endif

/*
 * Fix shmaddr, allocate descriptor, map shm, add attach descriptor to lists.
 *
 * NOTE! Despite the name, this is NOT a direct system call entrypoint. The
 * "raddr" thing points to kernel space, and there has to be a wrapper around
 * this.
 */
long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr, unsigned long shmlba)
{
    struct shmid_kernel *shp;
    unsigned long addr = (unsigned long)shmaddr;
    unsigned long size;
    struct file *file, *base;
    int err;
    unsigned long flags = MAP_SHARED;
    unsigned long prot;
    int acc_mode;
    struct ipc_namespace *ns;
    struct shm_file_data *sfd;
    int f_flags;
    unsigned long populate = 0;

    err = -EINVAL;
    if (shmid < 0) {
        goto out;
    }

    if (addr) {
        if (addr & (shmlba - 1)) {
            if (shmflg & SHM_RND) {
                addr &= ~(shmlba - 1); /* round down */

                /*
                 * Ensure that the round-down is non-nil
                 * when remapping. This can happen for
                 * cases when addr < shmlba.
                 */
                if (!addr && (shmflg & SHM_REMAP)) {
                    goto out;
                }
            } else
#ifndef __ARCH_FORCE_SHMLBA
                if (addr & ~PAGE_MASK)
#endif
                goto out;
        }

        flags |= MAP_FIXED;
    } else if ((shmflg & SHM_REMAP)) {
        goto out;
    }

    if (shmflg & SHM_RDONLY) {
        prot = PROT_READ;
        acc_mode = S_IRUGO;
        f_flags = O_RDONLY;
    } else {
        prot = PROT_READ | PROT_WRITE;
        acc_mode = S_IRUGO | S_IWUGO;
        f_flags = O_RDWR;
    }
    if (shmflg & SHM_EXEC) {
        prot |= PROT_EXEC;
        acc_mode |= S_IXUGO;
    }

    /*
     * We cannot rely on the fs check since SYSV IPC does have an
     * additional creator id...
     */
    ns = current->nsproxy->ipc_ns;
    rcu_read_lock();
    shp = shm_obtain_object_check(ns, shmid);
    if (IS_ERR(shp)) {
        err = PTR_ERR(shp);
        goto out_unlock;
    }

    err = -EACCES;
    if (ipcperms(ns, &shp->shm_perm, acc_mode)) {
        goto out_unlock;
    }

    err = security_shm_shmat(&shp->shm_perm, shmaddr, shmflg);
    if (err) {
        goto out_unlock;
    }

    ipc_lock_object(&shp->shm_perm);

    /* check if shm_destroy() is tearing down shp */
    if (!ipc_valid_object(&shp->shm_perm)) {
        ipc_unlock_object(&shp->shm_perm);
        err = -EIDRM;
        goto out_unlock;
    }

    /*
     * We need to take a reference to the real shm file to prevent the
     * pointer from becoming stale in cases where the lifetime of the outer
     * file extends beyond that of the shm segment.  It's not usually
     * possible, but it can happen during remap_file_pages() emulation as
     * that unmaps the memory, then does ->mmap() via file reference only.
     * We'll deny the ->mmap() if the shm segment was since removed, but to
     * detect shm ID reuse we need to compare the file pointers.
     */
    base = get_file(shp->shm_file);
    shp->shm_nattch++;
    size = i_size_read(file_inode(base));
    ipc_unlock_object(&shp->shm_perm);
    rcu_read_unlock();

    err = -ENOMEM;
    sfd = kzalloc(sizeof(*sfd), GFP_KERNEL);
    if (!sfd) {
        fput(base);
        goto out_nattch;
    }

    file = alloc_file_clone(base, f_flags, is_file_hugepages(base) ? &shm_file_operations_huge : &shm_file_operations);
    err = PTR_ERR(file);
    if (IS_ERR(file)) {
        kfree(sfd);
        fput(base);
        goto out_nattch;
    }

    sfd->id = shp->shm_perm.id;
    sfd->ns = get_ipc_ns(ns);
    sfd->file = base;
    sfd->vm_ops = NULL;
    file->private_data = sfd;

    err = security_mmap_file(file, prot, flags);
    if (err) {
        goto out_fput;
    }

    if (mmap_write_lock_killable(current->mm)) {
        err = -EINTR;
        goto out_fput;
    }

    if (addr && !(shmflg & SHM_REMAP)) {
        err = -EINVAL;
        if (addr + size < addr) {
            goto invalid;
        }

        if (find_vma_intersection(current->mm, addr, addr + size)) {
            goto invalid;
        }
    }

    addr = do_mmap(file, addr, size, prot, flags, 0, &populate, NULL);
    *raddr = addr;
    err = 0;
    if (IS_ERR_VALUE(addr)) {
        err = (long)addr;
    }
invalid:
    mmap_write_unlock(current->mm);
    if (populate) {
        mm_populate(addr, populate);
    }

out_fput:
    fput(file);

out_nattch:
    down_write(&shm_ids(ns).rwsem);
    shp = shm_lock(ns, shmid);
    shp->shm_nattch--;
    if (shm_may_destroy(shp)) {
        shm_destroy(ns, shp);
    } else {
        shm_unlock(shp);
    }
    up_write(&shm_ids(ns).rwsem);
    return err;

out_unlock:
    rcu_read_unlock();
out:
    return err;
}

SYSCALL_DEFINE3(shmat, int, shmid, char __user *, shmaddr, int, shmflg)
{
    unsigned long ret;
    long err;

    err = do_shmat(shmid, shmaddr, shmflg, &ret, SHMLBA);
    if (err) {
        return err;
    }
    force_successful_syscall_return();
    return (long)ret;
}

#ifdef CONFIG_COMPAT

#ifndef COMPAT_SHMLBA
#define COMPAT_SHMLBA SHMLBA
#endif

COMPAT_SYSCALL_DEFINE3(shmat, int, shmid, compat_uptr_t, shmaddr, int, shmflg)
{
    unsigned long ret;
    long err;

    err = do_shmat(shmid, compat_ptr(shmaddr), shmflg, &ret, COMPAT_SHMLBA);
    if (err) {
        return err;
    }
    force_successful_syscall_return();
    return (long)ret;
}
#endif

/*
 * detach and kill segment if marked destroyed.
 * The work is done in shm_close.
 */
long ksys_shmdt(char __user *shmaddr)
{
    struct mm_struct *mm = current->mm;
    struct vm_area_struct *vma;
    unsigned long addr = (unsigned long)shmaddr;
    int retval = -EINVAL;
#ifdef CONFIG_MMU
    loff_t size = 0;
    struct file *file;
    struct vm_area_struct *next;
#endif

    if (addr & ~PAGE_MASK) {
        return retval;
    }

    if (mmap_write_lock_killable(mm)) {
        return -EINTR;
    }

    /*
     * This function tries to be smart and unmap shm segments that
     * were modified by partial mlock or munmap calls:
     * - It first determines the size of the shm segment that should be
     *   unmapped: It searches for a vma that is backed by shm and that
     *   started at address shmaddr. It records it's size and then unmaps
     *   it.
     * - Then it unmaps all shm vmas that started at shmaddr and that
     *   are within the initially determined size and that are from the
     *   same shm segment from which we determined the size.
     * Errors from do_munmap are ignored: the function only fails if
     * it's called with invalid parameters or if it's called to unmap
     * a part of a vma. Both calls in this function are for full vmas,
     * the parameters are directly copied from the vma itself and always
     * valid - therefore do_munmap cannot fail. (famous last words?)
     */
    /*
     * If it had been mremap()'d, the starting address would not
     * match the usual checks anyway. So assume all vma's are
     * above the starting address given.
     */
    vma = find_vma(mm, addr);

#ifdef CONFIG_MMU
    while (vma) {
        next = vma->vm_next;

        /*
         * Check if the starting address would match, i.e. it's
         * a fragment created by mprotect() and/or munmap(), or it
         * otherwise it starts at this address with no hassles.
         */
        if ((vma->vm_ops == &shm_vm_ops) && (vma->vm_start - addr) / PAGE_SIZE == vma->vm_pgoff) {

            /*
             * Record the file of the shm segment being
             * unmapped.  With mremap(), someone could place
             * page from another segment but with equal offsets
             * in the range we are unmapping.
             */
            file = vma->vm_file;
            size = i_size_read(file_inode(vma->vm_file));
            do_munmap(mm, vma->vm_start, vma->vm_end - vma->vm_start, NULL);
            /*
             * We discovered the size of the shm segment, so
             * break out of here and fall through to the next
             * loop that uses the size information to stop
             * searching for matching vma's.
             */
            retval = 0;
            vma = next;
            break;
        }
        vma = next;
    }

    /*
     * We need look no further than the maximum address a fragment
     * could possibly have landed at. Also cast things to loff_t to
     * prevent overflows and make comparisons vs. equal-width types.
     */
    size = PAGE_ALIGN(size);
    while (vma && (loff_t)(vma->vm_end - addr) <= size) {
        next = vma->vm_next;

        /* finding a matching vma now does not alter retval */
        if ((vma->vm_ops == &shm_vm_ops) && ((vma->vm_start - addr) / PAGE_SIZE == vma->vm_pgoff) &&
            (vma->vm_file == file)) {
            do_munmap(mm, vma->vm_start, vma->vm_end - vma->vm_start, NULL);
        }
        vma = next;
    }

#else /* CONFIG_MMU */
    /* under NOMMU conditions, the exact address to be destroyed must be
     * given
     */
    if (vma && vma->vm_start == addr && vma->vm_ops == &shm_vm_ops) {
        do_munmap(mm, vma->vm_start, vma->vm_end - vma->vm_start, NULL);
        retval = 0;
    }

#endif

    mmap_write_unlock(mm);
    return retval;
}

SYSCALL_DEFINE1(shmdt, char __user *, shmaddr)
{
    return ksys_shmdt(shmaddr);
}

#ifdef CONFIG_PROC_FS
static int sysvipc_shm_proc_show(struct seq_file *s, void *it)
{
    struct pid_namespace *pid_ns = ipc_seq_pid_ns(s);
    struct user_namespace *user_ns = seq_user_ns(s);
    struct kern_ipc_perm *ipcp = it;
    struct shmid_kernel *shp;
    unsigned long rss = 0, swp = 0;

    shp = container_of(ipcp, struct shmid_kernel, shm_perm);
    shm_add_rss_swap(shp, &rss, &swp);

#if BITS_PER_LONG <= 32
#define SIZE_SPEC "%10lu"
#else
#define SIZE_SPEC "%21lu"
#endif

    seq_printf(s,
               "%10d %10d  %4o " SIZE_SPEC " %5u %5u  "
               "%5lu %5u %5u %5u %5u %10llu %10llu %10llu " SIZE_SPEC " " SIZE_SPEC "\n",
               shp->shm_perm.key, shp->shm_perm.id, shp->shm_perm.mode, shp->shm_segsz,
               pid_nr_ns(shp->shm_cprid, pid_ns), pid_nr_ns(shp->shm_lprid, pid_ns), shp->shm_nattch,
               from_kuid_munged(user_ns, shp->shm_perm.uid), from_kgid_munged(user_ns, shp->shm_perm.gid),
               from_kuid_munged(user_ns, shp->shm_perm.cuid), from_kgid_munged(user_ns, shp->shm_perm.cgid),
               shp->shm_atim, shp->shm_dtim, shp->shm_ctim, rss * PAGE_SIZE, swp * PAGE_SIZE);

    return 0;
}
#endif
